1. Field of the Invention
This invention relates to timber dapping apparatus, and more particularly to an improved timber dapping apparatus for cutting flat bottomed daps in heavy timber, with the flat bottom being disposed at a predetermined angle relative to the longitudinal axis of the timber.
2. Description of the Prior Art
It is frequently necessary to cut relatively wide, flat bottomed notches, commonly referred to as gains or daps, in heavy timber such as railroad ties, utility poles, bridge timber, and the like, and numerous devices and procedures have been developed in the past for cutting such notches. For example, numerous machines have been developed for adzing, milling or otherwise forming recessed surfaces in the top of railroad ties to act as seats for the rail plates employed to secure rails to the ties. Since the present invention is particularly well adapted for such use, it will be described herein as an apparatus for dapping or gaining railroad ties or crossties, it being understood that the invention is not so limited, and that the term crosstie should be interpreted to mean any heavy timber, beam or the like.
The prior art tie dapping apparatus generally has included means for feeding the ties transversely, i.e., in a direction perpendicular to their length, through a work station where two driven cutting heads engage the top surface to adz, mill, saw, or otherwise simultaneously form two daps. Frequently the dapping operation is followed, at a subsequent work station, by a boring operation where pilot holes are formed in a fixed pattern in the bottom surface of each dap for receiving and accurately locating rails spikes. One such apparatus is disclosed, for example, in U.S. Pat. No. 4,071,060 wherein ties are fed in intermittent steps through the apparatus by reciprocating feeding arms having a plurality of pivoted feed dogs mounted thereon. A pair of motor driven adzing heads are mounted at a first station for cutting a pair of transverse recesses in the upwardly directed surface of the crossties as they are moved therethrough. At a second station, motor driven boring tools are lowered to form pilot holes in the recessed surfaces. The adzing heads are adjustable vertically to control the depth of cut of the respective recesses.
U.S. Pat. No. 1,704,273 also discloses a machine for adzing and boring railroad ties in which the ties are advanced through the apparatus in a direction perpendicular to their longitudinal axis. Two separate feeding mechanisms are provided, one to advance the ties through an adzing station, and the other through a boring station. Each feeding mechanism includes a reciprocating dog arrangement for engaging each end of the tie, and clamping means is provided to firmly hold the tie during the adzing operation.
A hand controlled pole gaining apparatus is disclosed in U.S. Pat. No. 2,521,457 wherein utility poles are conveyed longitudinally past a driven gaining head. The pole is stopped at the desired position and the gaining head is manually lowered and reciprocated across the stationary pole to cut the gain.
U.S. Pat. No. 901,681 discloses a router type rotary cutting head for use in a tie gaining apparatus. Although details of the apparatus are not disclosed, the patent states that the vertical shaft of the cutting head may be inclined slightly relative to the vertical so as to adapt the gain to receive an inclined base or foot of a rail.
It is also known to cut a dap in a railroad tie with the recessed flat surface of the dap being disposed at an accute angle relative to the longitudinal axis of the beam by initially elevating one end of the tie to an angle relative to the horizontal corresponding to the desired angle of the recessed surface of the dap. The tie is clamped and held in this position and a cutting head is moved across the tie to cut the dap. When using this apparatus to cut a dap having a width, measured longitudinally of the tie, greater than that made by a single pass of the cutting head, it is necessary to make a first pass with the cutter head, then lower and move the tie longitudinally the desired distance, then again raise and clamp it at the desired angle. This procedure is not only very time consuming, but great difficulty is encountered in maintaining the flat bottom surface cut by two passes in exactly the same plane.
While the prior art gaining or dapping devices have met with some success and have been used for many years, they have not been entirely satisfactory for various reasons. For example, the machines adapted to simultaneously dap both ends of a tie generally have not been operable to cut the daps at different depths while forming the bottom surface of such daps in a common plane inclined relative to the longitudinal axis of the tie as required, for example, to bank a track in a curve. Further, such devices generally have not been readily adjustable to form daps of different widths while assuring that the bottom surface of a wide dap made by multiple passes of the cutter head will be completely flat.
It is, therefore, the primary object of the present invention to provide an improved timber dapping apparatus which overcomes the foregoing and other drawbacks of the prior art.
Another object of the present invention is to provide a timber dapping apparatus which may be employed to form daps of various widths without requiring changing of the cutting elements.
Another object of the invention is to provide a timber dapping apparatus in which a cutting head may be moved in a direction parallel to the longitudinal axis of a timber positioned in the apparatus and in which the cutting head may make multiple passes across the timber to form a dap having a width greater than the width of the cutting element.
Another object of the invention is to provide such an apparatus wherein the cutting head may be pivotted about an axis extending transversely of and spaced from the longitudinal axis of a timber in the apparatus whereby the bottom surface of a dap cut in the timber extends at an angle inclined relative to the longitudinal axis of the timber.